large diameter seals

ABSTRACT

A large diameter seal having a band of elastic material on its outer diameter to insure a complete and effective sealing in the counterbore and a method for manufacturing this large diameter seal having elastomeric material on its outer diameter.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of co-pending U.S. patent applicationSer. No. 11/427,381, entitled METHOD OF MAKING IMPROVED LARGE DIAMETERSEALS, filed on Jun. 29, 2006, which is hereby incorporated herein inits entirety by reference.

BACKGROUND OF THE INVENTION

The present invention relates to large diameter seals and, moreparticularly, to large diameter seals having thin, pliable coatings ontheir outside diameters, and methods of making such seals. In general,this process can be performed on any so-called assembled seal.

Ordinary oil seals of from, perhaps, one inch to six inches in diameter,are made from a rigid casing and have bonded rubber lips of variouskinds. Such seals are usually produced by compression molding, transfermolding or injection molding the rubber portion onto a steel, aluminumor like casing. Large diameter seals, for example, those of eight inchesto sixty inches or more in diameter, are far too big to be economicallymanufactured by such a molding process. In other words, trying to injectrubber in a mold having an inside diameter of at least eight inches, butusually 12 inches up to 60 inches or more in diameter, would be veryawkward, expensive, and impractical. To make such a mold would beextremely costly, especially considering that the mold would ordinarilybe very seldom used.

In a regular or small diameter oil seal, the casing is made from astamping or drawing. Such seals have either a metal or rubber OD(“outside diameter”). However, a large diameter seal is customarily madeby a different method, with such method involving forming the casing inone step by a spinning operation, wherein the two radial flangessurround a major or axial portion of the casing. Thus, the casing isformed by placing a ring of metal in a spinning apparatus and spinningor bending the flanges thereon to form a generally U-shaped casing, asis well known in the art.

Thereafter, a portion of the elastomeric seal body is formed separately,cut into whatever overall length is desired, the end portions are bondedto each other to create a closed loop, and thereafter, the elastomericportion is placed within the casing, and secured thereto by clinching.The resulting seal, which may be made with or without a garter spring,or in some cases with an embedded garter spring, is then ready to beused.

However, the present invention uses a different method. The seal isdesired to have a rubber outside diameter (OD), for several importantreasons. Installing a large diameter seal in a seal-receiving area,customarily a counterbore on a large machine such as a the rollers in apaper mill, steel mill or some other such application, because of thesize of the seal, is customarily difficult. When the seal is evenslightly too small for the application, it allows leakage between thecounterbore and the OD of the casing. This is also the case withirregularities in the surface. If the seal is too large, the seal isunable to be installed, because the line-to-line contact necessary isextremely difficult to obtain. It is customary for such a large diameterseal-receiving area to be required to be free from nicks, scratches orthe like, and as a result, installing such seals correctly becomes amajor operation, particularly if the machine on which it is to beinstalled is old or has suffered from lack of maintenance.

Consequently, there has been a desire to manufacture a large diameterseal which would enable the secondary seal or the outside diameter ofthe seal to the counterbore to be completely and effectively sealed.Such a seal would also require a chamfer on at least one surface of itsoutside diameter, in addition preferably to being made from anelastomeric material which would be able to accommodate a slightout-of-round condition or other irregularities in the seal-receivingcounterbore.

Accordingly, it is an object of the present invention to provide animproved large diameter seal.

Another object is to produce a large diameter seal, which includes aband of elastomeric material on its outside diameter.

Another object is to provide a method of creating an outside diameterrubber seal without creating a large-diameter mold, and which would notrequire equipment other than that required to make the remainder of theseal itself.

A still further object would be to provide a seal which wouldaccommodate small imperfections in the installed or outside diameter,including an out-of-round condition or having nicks or otherirregularities in the OD.

A still further object is to provide a method which involves creating anelastomeric seal band by bonding the end portions of a continuous stripof thin, elastomeric material into a closed loop, placing a bondingadhesive on the casing, and thereafter stretching the rubber band thusmade into a larger diameter, allowing it to spring back and cling to theoutside diameter of the casing, and then trimming one or both edges toprovide a chamfer to accommodate and simplify the installation of such aseal.

A further object of the invention is to provide a rubber OD on a sealwhich would thereafter allow for improved ease of installation andremoval, and would not damage the customer's hardware.

An object of the invention is to develop a rubber material for the OD ofa seal which allows a certain amount of compression set duringinstallation but thereafter remains resilient indefinitely.

Another object would be to provide an improved, rubber outside diameterseal which is especially useful in steel production, mining, pulp andpaper and other industries generally requiring large diameter seals.

A still further object would be to provide a large diameter seal havinga greatly reduced press-in or installing force, and a reduced extractionforce.

A related object is to provide a seal which can be reinstalled withoutleaking in the application after removal from the counterbore.

Another object is to provide a seal which could compensate for anout-of-round or worn condition of the counterbore in which it isreceived.

A further object is to provide a seal which will not cause any damage toits associated counterbore, even during extraction.

A still further object is to provide a seal which has an outsidediameter lead-in chamfer or radius.

SUMMARY OF THE INVENTION

The invention achieves its objects and others by providing an improvedseal and method for making it, including unrolling a portion of rubbershim stock, cutting the shim stock to a smaller length than thatrequired to encircle the outside diameter of the seal, bonding the endstogether, stretching the seal over the casing, bonding shim stock to thecasing and thereafter trimming the rubber to impart chamfers to one orboth sides, thereby compensating for worn or out-of-round conditions orimperfections in the counterbore in which it is to be installed, andwhich therefore eliminates any damage to the bore during subsequentextraction.

The exact manner in which these advantages and objects and others whichare inherent in the invention are achieved in practice will become moreclearly apparent when reference is made to the following detaileddescription of the invention set forth by way of example and shown inthe accompanying drawings in which like reference numbers indicatecorresponding parts throughout.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of the so-called rubber shim stock,which is received in large diameter coils and of which a portion isshown just beginning to be unrolled from the coil;

FIG. 2 schematically illustrates plural, equal lengths of the rubbershim stock being cut after being taken from the coil;

FIG. 3 is a schematic vertical sectional view of the rubber shim stock,showing liquid adhesive being affixed to the two end portions thereof,and showing the shim stock about to be formed into a circular loop;

FIG. 4 is a schematic vertical sectional view showing the end portionsof the rubber shim stock when the ends are fully bonded to each other toform a circular loop;

FIG. 5 schematically shows a circular piece of rubber shim stock beingstretched to a larger radius so as to fit over a casing, showing themanner in which the liquid adhesive is added to the OD of the metalcasing, and showing the rubber shim stock in the process of beingallowed to return to just more than its totally relaxed diameter;

FIG. 6 is a vertical sectional view of a seal casing with the rubbercomprising the seal body already inserted into the steel casing andbonded in place;

FIG. 7 shows the casing with the rubber shim stock bonded thereto by theuse of the adhesive shown in FIG. 5, and;

FIG. 8 shows the rubber OD being trimmed to impart a chamfer to the shimstock on both axial sides of the seal.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

While the invention may be practiced by the illustrated methods or bysomewhat different methods, and the seal made thereby has severalfeatures of novelty, an illustration will be given of one preferredmethod of making a seal, and the resulting seal having a rubber OD witha selected amount of shim stock bonded thereto.

Referring now to the drawings in greater detail, there shown in FIG. 1 acoil generally designated 20 of rubber so-called shim stock 22. Thisshim stock 22 is shown as being unrolled at 24 wherein an individualpiece is taken from a much longer roll. It will be understood that thisdrawing is schematic and that the shim stock in question, usually 0.094inches in thickness, comes in several hundred foot lengths. In thiscase, for illustration, the shim stock is cut into two individual pieces26, 28, (FIG. 2) each having end portions 30, 32 spaced apart inselected, predetermined lengths. The lengths 26, 28 of each section ofshim stock are treated successively. In FIG. 3, there is shown one suchpiece 26 having two end portions 30, 30 in the presence of a liquidadhesive 34. The first liquid adhesive 34 is a powerful, contactadhesive which enables the two ends 30, 30 to be bonded together into acontinuous loop 36 as shown in FIG. 4.

FIG. 4 shows the completed loop 36 made by bonding two ends of the loop30, 30 together. FIGS. 5, 6 and 7 show the next steps in the process.FIG. 6 is a drawing showing a cross section of a large diameter seal.Here, there are shown the main components of a large diameter seal,namely, the body generally designated 38, and including frusto-conicalair and oil side surfaces 40, 42 meeting along a line of intendedcontact 44 with the shaft 45. These surfaces are sometimes referred toas the inside face, or oil side 42 of the seal, and as the outside face,or air side 40 of the seal. The seal body of 38 is shown to include acurvilinear, generally somewhat circular, contoured opening 46 and anupper or radially outward portion 48 of the seal body 38. This seal bodyor elastomeric portion 38 is received within a casing generallydesignated 50 and shown to include a principal, axial portion 52 and apair of radial flanges 54, 56.

These flanges 54, 56 are produced by spinning the an originally flatportion 52 until the correct curvature and the desired flanges 54, 56are obtained. Thereafter, the seal body 38 is formed and placed withinthe casing generally designated 50. Needless to say, the seal could bereversed and the flanges directed outwardly.

Referring now to FIG. 5, there is shown a stretched portion of rubbershim stock surrounding the portion 52 of the casing. The rubber portion26 is shown as being somewhat spaced apart from the axial portion 52 ofthe casing. Liquid adhesive 58 is shown schematically as being depositedon the axial portion 52 of the casing, and the piece of shim stock 26 ashaving had its end portions secured together. A loop 26 is then formedand the loop 26 having been stretched to a larger diameter than that ofthe flange 52. The forces holding the shim stock spaced apart from theflange 52 are then released, allowing the shim stock 26 to contact thecasing 50 through the adhesive. In FIG. 7, it is shown that the shimstock is now bonded to the casing, and has become a permanent fixture.

Referring now to FIG. 8, there are shown two knives 60, 62, which arepositioned spaced apart but adjacent the edge portions 66, 68 of theshim stock, and they are thereafter moved into position so as to trimthese edges 64, 66. This cuts out small strips 68, 70, from the shimstock 26 overlying the axial portion 52 of the casing 50. Thereupon, thenew large diameter seal is ready for installation.

Referring now to certain aspects of the invention and the method ofperforming it, preferably the rubber used is initrile (Buna N) rubber,but other synthetic rubbers and other rubbers such as natural rubber,silicone rubbers and other kinds of rubber could be used. The adhesive34 used is a fast setting, clear cyanoacrylate adhesive, which bonds therubber ends together and which is further identified as aroom-temperature curing adhesive, for example, Locktite 420. This rubberis ready for the next step almost immediately. This loop of rubber isthen sanded lightly to render the surface suitable for bonding with thenext adhesive. The rubber is stripped of any residual oil.

The second process starts by cleaning the metal of any oil, etc. used informing the metal casing. Next, applying the rubber to the casing 50—isdone by applying a similar adhesive—Locktite brand 4212 or 4211, to themetal casing. Both adhesives are described as thermally resistant (250°F.) high viscosity toughened adhesives. The next step involvesstretching the one-piece band 26 of rubber to about 105% to 125% of itsrelaxed length, and covering the casing with such rubber band. Therubber should have no less length than 102%, and up to 110%, of thelength in its relaxed condition. The bond will form in about 5 minutes,and the joint is then allowed to cure for 24 hours.

After a suitable curing period of 24 hours or more, the knives or razorblades may be used to trim the chamfer on one or both sides of therubber OD coating. Normally, this is done by placing the inclined bladeon the edge of the casing and rotating the casing until the margin ofthe rubber have been trimmed off. A 30 degrees from the horizontal ispreferred.

It will thus be seen that the invention provides a novel seal and methodhaving a number of advantages and characteristics, including thoseherein pointed out and other which are inherent in the invention.

1. An assembled oil seal including a generally U-shaped metal casinghaving a pair of radial side flanges, each flange being attachedintegrally to an axially extending end portion, said metal casing havinga first elastomeric component in the form of a seal lip received thereinand crimped permanently to each of the interior surfaces of said flangesand said end portion, said seal lip having frusto-conical air and oilside surfaces meeting along a seal band of intended contact with anassociated shaft, said seal also having bonded to an exterior surface ofsaid end portion of said casing, a second elastomeric component in theform of a thin, continuous strip of an elastomer, said secondelastomeric component having a thickness of at least 0.02 inches and notmore than 0.125 inches, said second elastomeric component having both ofits end portions permanently bonded to each other, said secondelastomeric component being thereby stretched when installed to at least102% of its length in a relaxed condition.
 2. An oil seal as defined inclaim 1 wherein said seal has an outside diameter of at least 8 inches.3. An oil seal as defined claim 1 which includes a garter springreceived within said first elastomeric lip.
 4. An oil seal as definedclaim 1 wherein said second elastomeric component has a thickness offrom about 0.06 inches to about 1.0 inches.
 5. An oil seal as definedclaim 1 wherein said residual stress in said second elastomericcomponent is 103% to about 110% of the stress in a relaxed condition.